Field of the Invention
The invention relates to a two-chamber engine mount, especially for motor vehicles, including a housing having an interior accommodating a supporting spring made an elastomeric material dividing the interior into a working chamber and a compensating chamber closed off from the surroundings by an elastomeric diaphragm, the working chamber and the compensating chamber being filled with a hydraulic fluid and connected to each other through an overflow passage.
One such two-chamber engine mount is known from European Patent Application 0 253 373 A1. In that known two-chamber engine mount a supporting spring of an elastomeric material is accommodated in a cylindrical housing. The supporting spring divides the interior of the housing into a working chamber and a compensating chamber disposed at an outer periphery of the supporting spring. The two chambers are connected through an overflow passage. A mount core which is vulcanized in place in the supporting spring is to be secured to an engine. A flange which is applied to the mount core clasps the outside of the housing with a clearance and serves as an axial stop. The flange is an additional component which complicates assembly and simultaneously increases the weight and overall dimensions of the mount.
It is accordingly an object of the invention to provide a two-chamber engine mount, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which is further developed so that a radial stop is provided for a supporting spring while achieving compact dimensions and facilitated assembly.
With the foregoing and other objects in view there is provided, in accordance with the invention, a two-chamber engine mount, especially for motor vehicles, comprising a housing having an interior; a supporting spring of an elastomeric material disposed in the interior and dividing the interior into a working chamber and a compensating chamber to be filled with a hydraulic fluid; an overflow passage interconnecting the working chamber and compensating chamber; an elastomeric diaphragm closing off the compensating chamber from the surroundings; and at least one plunger disposed in the compensating chamber as a radial stop.
The plunger provided in accordance with the invention improves the acoustic response in the higher frequency range, more particularly in the frequency range between 80 and 160 Hz. The plunger results in a considerable reduction in the dynamic stiffness in the desired frequency range, often down to a value below that of the static stiffness. This reduction is termed high-frequency isolation. At the same time the plunger acts as a radial stop.
In the two-chamber engine mount in accordance with the invention the working chamber is advantageously defined by the supporting spring and the housing. The compensating chamber surrounds the working chamber and is defined by the supporting spring, the housing and an elastomeric diaphragm. Such a mount is also termed a xe2x80x9cpot mountxe2x80x9d.
In accordance with another feature of the invention, the plunger is integral with or formed as one piece with the supporting spring. The integral configuration facilitates producing and assembling the two-chamber engine mount in accordance with the invention. The plunger is vulcanized in place with the mount core in a single operation during production.
In accordance with a further feature of the invention, the plunger is separate from the supporting spring on an outer wall surface of the compensating chamber. Although the plunger is produced as a separate component in this embodiment, placing it at the outer wall surface of the compensating chamber is speedy and facilitated.
In accordance with an added feature of the invention, there is provided a combination of these two plunger configurations. In this case a plunger configured integrally with the supporting spring cooperates with a plunger disposed at the outer wall surface of the compensating chamber.
In all of the embodiments the plunger or plungers achieve high-frequency isolation. A plunger gap formed between the plunger and the outer wall surface of the working chamber or the supporting spring or between the two plungers is significant in this regard. The dimensions of this plunger gap are a factor significantly characterizing the high-frequency isolation.
The parameters referred to as plunger diameter, plunger gap and gap length, which are significant in dictating the dynamic response, are freely selectable by placing the plunger in the compensating chamber. When use is made of a plunger disposed at the supporting spring, the plunger gap is formed between the plunger and the outer wall surface of the compensating chamber. This plunger gap is independent of the position of the plunger, thus achieving a dynamic response independent of the settlement of the hydro-elastic mount.
In accordance with an additional feature of the invention, the plunger is shiftingly guided at the outer wall surface in the direction of a centerline through the engine mount. This enables stops or fastener elements for the plunger to be eliminated and thus facilitates assembly and reduction of weight without detriment to the dual function of the plunger as a radial stop and for high-frequency isolation.
In accordance with yet another feature of the invention, the plunger includes a leaf spring vulcanized in place to boost the radial stiffness. The leaf spring may be simply vulcanized in place in the plunger to enable the radial stiffness to be xe2x80x9ctunedxe2x80x9d to the existing boundary conditions.
In accordance with yet a further feature of the invention, there is provided at least one axial stop to define the movement of the supporting spring in the direction of its centerline. The axial stop prevents prohibitively large movements of the supporting spring in avoiding the engine mount from being damaged or ruined.
In accordance with yet an added feature of the invention, the axial stop is configured as a protruding portion of a bottom of the housing, requiring no additional components, thus simplifying production and assembly of the two-chamber engine mount in accordance with the invention.
In accordance with yet an additional feature of the invention, the axial stop is rigidly connected to the housing from which it protrudes radially. The outer diameters of the two-chamber engine mount in accordance with the invention are thus maintained compact.
Advantageously, both axial stops are combined in such a way that they define the movements of the supporting spring in two opposing directions, thus preventing prohibitive movements of the supporting spring in the direction of both the engine and the vehicle body.
Advantageously the first axial stop cooperates with a projection configured integrally with the supporting spring, and the second with a plunger configured integrally with the supporting spring. The projection and the plunger may be vulcanized in place in a single operation with the mount core in producing the supporting spring.
In accordance with again another feature of the invention, the supporting spring has a gap in which a movable isolation diaphragm is accommodated with clearance. This isolation diaphragm, like the plunger, results in a reduction in the dynamic stiffness in a specific frequency range.
Advantageously, the plunger is configured in such a way that it results in a high-frequency isolation in a first frequency range while a high-frequency isolation is achieved in a second frequency range by the isolation diaphragm, thus achieving an improvement in the acoustic response in two frequency ranges that are separate from each other. As an alternative the isolation diaphragm and the plunger may be constructed for a high-frequency isolation in the same frequency range so that the dynamic stiffness is significantly reduced.
In accordance with again a further feature of the invention, the isolation diaphragm and the gap are disposed parallel to a centerline of the engine mount. The term xe2x80x9cparallelxe2x80x9d in this sense is understood to mean that the isolation diaphragm and the gap are oriented perpendicular to the plane which in turn stands perpendicular to the centerline of the engine mount. This embodiment permits a configuration and assembly which is simple.
In accordance with again an added feature of the invention, the isolation diaphragm has the shape of a ring segment. The isolation diaphragm and the gap in this embodiment are disposed concentric to the centerline of the engine mount.
In accordance with again an additional feature of the invention, the supporting spring forms ridges defining the gap and passages located in-between for fluid actuation of the isolation diaphragm. These ridges assure the stability of the supporting spring. The stability is difficult to achieve with a large full-length opening for fluid actuation of the isolation diaphragm. At the same time the passages between the ridges permit a relatively large surface area fluid actuation of the isolation diaphragm.
In accordance with a concomitant feature of the invention, the isolation diaphragm is made of an elastomeric material, a substantially rigid material or a combination of these materials. The isolation diaphragm can be optimally xe2x80x9ctunedxe2x80x9d to the various boundary conditions by suitably selecting the material therefor.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a two-chamber engine mount, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.